by Ben Bova
The extremophiles have taught astrobiologists an enormous lesson: Until this past decade, the astronomers, biologists, and other investigators who had been seeking life on other worlds were all victims of a false assumption. They tacitly assumed that they should search for life on the sunlit surface of worlds where liquid water might exist. The extremophiles have shown that life is much tougher, much more ubiquitous, than anyone had previously imagined.
Not only does Gold’s deep, hot biosphere really exist here on Earth, but deep, hot biospheres may be more plentiful than life on planetary surfaces, where organisms must face hard radiation, harsh weather, and extremes of cold and heat.
Biologists now speculate that the total mass of living matter in that dark, hot underground environment beneath our feet may well be equal to the total tonnage of living matter on the surface of our world.
And if our planet has a deep, hot biosphere, what about other worlds?
The three requirements for life are still valid, even for the extremophiles: Life needs a building-block molecule, a medium in which chemical reactions can take place, and energy. The extremophiles are built on molecular chains of carbon and require water, just as we do. Carbon is the best building block we know of, and it is abundant in the universe. Water is the best medium we know, and it is also abundant. But the energy for life need not be restricted to sunlight or the light of another star. It can be the heat energy welling up from a planet’s molten core. Or perhaps even the energy from radioactivity.
This realization has been a watershed in thinking about life. The discovery of extremophiles has stretched the “hunting ground” in which scientists can search for life beyond the Earth. As we will see in Chapter 13, there is some evidence that fossils of microbial life have been found inside meteorites that were blasted out of the crust of Mars millions of years ago. The evidence is far from conclusive; in fact, it is hotly debated. But for the first time, astrobiologists are examining the possibilities of life existing beneath the surface of another world.
Moreover, the extremophiles are also telling us a great deal about how life arose on this planet of ours.
5
The Great Mindshift:Exobiology BecomesAstrobiology
Something we were withholding made us weak
Until we found out that it was ourselves
We were withholding from our land of living . . .
—Robert Frost
The Gift Outright
SIXTY-FIVE MILLION YEARS AGO, a meteor the size of Manhattan Island slammed into the Earth with such force that the explosion and its aftermath shattered the global environment, wiping out the dinosaurs and more than a third of all the species living on the planet. Paleontologists call that catastrophe the K/T extinction event.
The field of astrobiology owes its birth to a different sort of extinction event.
In 1994, as part of Vice President Al Gore’s National Performance Review (popularly called “reinventing government”), NASA was ordered by the White House to cut $5 billion from its planned budgets for the next five years. This triggered a paroxysm of self-examination known as the Zero-Base Review because the NASA internal review team started their work by assuming that nothing was sacred: Everything in the space agency was being subjected to keen budgetary scrutiny. By the spring of 1995, the review team proposed to NASA’s top management “sweeping management and organizational changes designed to simplify operations, reduce overlap, and cut spending . . . all without curtailing space and aeronautics programs.”
The study determined that the way to produce a “leaner and meaner” NASA was to prune the agency’s infrastructure, which meant that jobs, facilities, and administrative overhead must all be cut.
One of the Zero-Base Review team’s recommendations was that the Ames Research Center be closed down. Completely.
THE AMES RESEARCH CENTER
Ames is located at Moffett Field, California, nestled in the low hills of Silicon Valley along the Pacific coast, almost an hour’s drive south of San Francisco, near Palo Alto and Stanford University.
Moffett Field was originally a Navy base, named after Admiral William A. Moffett, a pioneer of naval aviation. The center is still dominated by enormous hangars that once housed huge dirigibles, such as the Los Angeles and the Macon, in the 1930s. During World War II, smaller blimps rode out over the Pacific on anti-submarine patrol.
The National Advisory Committee for Aeronautics built gigantic wind tunnels at Moffett Field in the 1940s to test new aircraft designs as World War II approached America. The facilities were named after Joseph Sweetman Ames, then head of NACA. In 1958, when NACA was incorporated into the newly formed National Aeronautics and Space Administration, the Ames Research Center became a major NASA facility, with expertise in aerodynamics, biology, and computer sciences. In 1994, the Navy base was closed and NASA took control of all of Moffett Field’s extensive facilities.
Ames became a focal point for cutting-edge research in space biology, computer sciences, and the arcane field of nanotechnology. Aeronautics researchers continued to use the wind tunnels until they were shut down, victims of budget-cutting from Washington—and of the growing power of computers to simulate flight conditions without the need for wind-tunnel verification.
In 1995, the entire base was scheduled for termination. Ames was to be closed down for good. But the scientists who treasured the campus-like atmosphere of Ames believed their work was too important to be thrown away; they fomented a rebellion born of desperation.
“Ames is always on the brink of extinction,” says Wesley Huntress, who was at that time NASA’s associate administrator for space science. Soft-spoken yet capable of quiet good humor, Huntress explains that Ames has always been something of an anomaly within the space agency, a very good group of scientists, but it’s not the agency’s top center for either aerodynamics or space exploration.
NASA’S HIERARCHY OF CENTERS
NASA is built around its centers. Critics claim the agency is not an organization so much as a collection of fiefdoms.
The Kennedy Space Center is the prime launch complex, of course. The Johnson Center, near Houston, is responsible for human space flight missions. The Marshall Center in Huntsville, Alabama, primarily develops space transportation hardware, such as the Saturn rockets that sent astronauts to the Moon and, more recently, components of the International Space Station. The Goddard Space Center in Maryland deals mainly with space physics and astrophysics; the major orbiting astronomical observatories are in Goddard’s purview, including the Hubble Space Telescope.
NASA’s Langley Center in Virginia has been the leader in aerodynamics research since the old NACA days. The Glenn Center near Cleveland (originally called the Lewis center) works on aircraft propulsion development. JPL, the Jet Propulsion Laboratory, in Pasadena has done most of NASA’s planetary exploration programs, such as Viking, Pioneer, Magellan, Voyager, and the more recent probes sent to Mars.
Ames seemed to be the “odd man out.” The center had done excellent aerodynamics research, but Langley was NASA’s lead facility for aerodynamics. Ames had acquired significant capabilities in computers and information technology, biology, and the new field of nanotechnology, where the hope is to be able eventually to build working machines the size of viruses.
But in 1995 Ames had no particular specialty to call its own, no area of expertise in which it was clearly NASA’s leading center—except for biology. Biology, however, was not one of NASA’s hot-button interests. (Human physiology, especially how the human body reacts to weightlessness, is, of course, of vital interest to NASA. The Johnson Space Flight Center was and still is the leader in that area.)
THE BIRTH OF ASTROBIOLOGY
Threatened with extinction, Ames’ scientists and managers conducted their own internal review. They asked themselves this question: What can we do that no other center can do and is important to NASA’s goals? In essence, they were wondering how they could evolve into an organization that can avert e
xtinction.
They invited Huntress to join their deliberations. Huntress, then associate administrator for space science at NASA Headquarters, knew the Ames researchers well. He had done his Ph.D. work at Stanford University under Nobel laureate Cyril Ponnamperuma (1923–1995), a pioneer in studies of the prebiotic chemistry that led to the origin of life. Huntress’ doctorate degree is in chemical physics, but he considered himself an astrochemist and still does.
As the Ames group deliberated its own future, it became clear that the center’s expertise in biology and computer sciences could be applied to studies of life in the universe. But NASA already had an exobiology program. How would the Ames effort differ from what was already being done?
In Huntress’ words, “Ames had the biology capability, but how to articulate it to NASA’s management in Washington? How to find a place for it in the organization chart?”
The Ames scientists felt that NASA’s exobiology program, good as it was, was too narrowly focused on astronomy and planetary geology, without enough emphasis on biology. They wanted to tackle the entire question of how life began and where it might be found beyond the Earth. They were interested in understanding the fundamental role of life in the universe. Huntress is credited with suggesting that they name the new effort astrobiology, although he maintains that one of the Ames researchers might have originally hit upon that word. Whichever, the task now became to decide what astrobiology should include and how it could be differentiated from the existing exobiology work.
Who Said It First?
ASTROBIOLOGY VS. EXOBIOLOGY
Since the 1960s NASA has had a program in exobiology, aimed at seeking evidence of life on other worlds. SETI had been part of the exobiology program until Congress cut all funding for the search for extraterrestrial intelligence.
When seeking life on other worlds, the first questions are the following: Where do we look? What are we looking for? When the exobiology program began, the only answers that anyone could give were: Look for a planet like Earth; look for the kind of life we can recognize.
Exobiology was, therefore, dominated by astronomy and geology. Its major efforts have been focused on finding planets that might support the kind of life we are familiar with and then looking for evidence that such life might exist there. Mars was an obvious candidate and still is. The 1976 Viking missions to Mars carried apparatus designed to detect metabolism similar to the metabolic processes of earthly organisms. With the hindsight of the ensuing quarter century, such an approach was “naive” in Huntress’ words.
Meanwhile, a flood of new discoveries and ideas was sweeping the scientific world in the 1990s. The Human Genome Project successfully mapped all of our genes. Possible evidence for fossilized bacteria was found in a meteorite that came from Mars. Planets circling other stars were discovered. Jupiter’s moon Europa showed that it might harbor an ocean of liquid water beneath its icy crust. Extremophiles showed that life on Earth could exist in environments that had previously been thought to be impossible. The Hubble Space Telescope and other orbiting astronomical observatories such as COBE (COsmic Background Explorer) peered back to the very beginnings of our universe.
Awash in the excitement of these discoveries, in September 1996, Ames hosted the First Astrobiology Workshop, to which were invited leading researchers in astronomy, biology, geology, and other physical sciences, as well as sociologists, psychologists, teachers, and philosophers. About two hundred people attended the conference, a turnout that stunned Ames’ people; they had invited eighty participants.
“This [astrobiology] was a revolution that everybody joined,” says Ames researcher Lynn Harper. Delighted by the enthusiasm and spirit of cooperation shown at the workshop, she remarked, “There wasn’t any of the usual status quo resistance or competition from existing programs.”
The workshop participants began the task of outlining the basic scientific content of astrobiology. Subsequent workshops, such as the 1998 Astrobiology Roadmap Workshop, refined the newborn field’s subject matter.
ASTROBIOLOGY’S DOMAIN
From the first, astrobiology was based on a shift in attitudes. Instead of concentrating on a search for Earth-like worlds and Earth-like life, the new paradigm of astrobiology recognized that we don’t understand life well enough to know what we should be looking for or where we should be looking. To search meaningfully for extraterrestrial life, astrobiologists realized that we must understand the origins and limits of life on Earth.
Astrobiology also encompasses the future of life in the universe. How do living creatures alter their environments? How does a planet’s biosphere alter that world? Will humans be able to live in habitats beyond the Earth? On other worlds? All this is part of the domain of astrobiology.
The workshop participants quickly realized that astrobiology must encompass nothing less than the study of all the aspects of life in the universe. In the words of David Morrison, director of space sciences at Ames and eventually to be named chief scientist of the Astrobiology Institute, “Astrobiology addresses three basic questions:
“How did life begin and evolve? (Where did we come from?)
“Does life exist elsewhere in the universe? (Are we alone?)
“What is life’s future on Earth and beyond? (Where are we going in space?)”
This agenda was much wider and deeper than exobiology’s search for habitable planets. The exobiology work is an important part of astrobiology’s goals; there is no fundamental conflict between the two programs. However, in the practical world of budgets and egos, some friction is to be expected.
Astrobiology is inherently multidisciplinary. As Morrison points out, it encompasses specialists in the earth sciences, life sciences, and space sciences, “including microbiology, ecology, molecular biology, paleontology, astronomy, planetary science, and chemistry.”
The 1996 workshop and subsequent meetings developed ten scientific goals for astrobiology:
1. Understand how life arose on Earth. Is life a unique phenomenon, restricted to our one world? If not, understanding the origins of life on our planet will help us to identify the conditions we should look for in seeking life on other planets.
2. Determine the general principles governing the organization of matter into living systems. How do nonliving chemicals become living organisms?
3. Explore how life evolves on the molecular, organism, and ecosystem levels. Understanding the processes of life from molecular to planetary scales will not only be pricelessly valuable for our own use here on Earth, but will help us to determine the specific clues (biomarkers) we should look for when examining other planets for signs of life.
4. Determine how the terrestrial biosphere has coevolved with the Earth. Life does not exist separate and apart from its environment. Life has changed our planet, and it will presumably change any planet on which it takes root.
5. Establish limits for life in environments that provide analogues for conditions on other worlds. Once it was thought that life could only be found on the sunlit surfaces of planets that held liquid water. The extremophiles have taught us that life’s possible environmental conditions are much broader than that. How extreme can conditions be and still be suitable for life? What are the “edges of the envelope” for life-bearing environments?
6. Determine what makes a planet habitable and how common these worlds are in the universe. There are more than a hundred billion stars in the Milky Way galaxy. How many of them harbor planetary systems? How many of these planets might be capable of supporting life?
7. Determine how to recognize the signature of life on other worlds. What are the biomarkers that signal the existence of life? Should we look for Earth-sized planets with free oxygen in their atmospheres? Or ice-clad worlds that are heated from within? Should we seek the “signature” of chlorophyll in the light from a planet, or evidence of running water across its terrain? Or all of the above?
8. Determine whether there is (or once was) life elsewhere in our solar sy
stem, particularly on Mars and Europa. Current observations indicate that Mars and Jupiter’s moon Europa are the two most likely places for us to find life. Several spacecraft missions are aimed at Mars; the one planned for Europa was canceled in NASA’s 2002 spasm of budget-cutting.
9. Determine how ecosystems respond to environmental change on time scales relevant to human life on Earth. Since the earliest farmers, we humans have been changing the landscape, the atmosphere, and the oceans of our world. Not only is understanding the effects of these changes important to our own survival on Earth, but such an understanding can help us to determine what we should look for when seeking evidence of intelligent life on other worlds.
10. Understand the response of terrestrial life to conditions in space or on other planets. Can organisms (including humans) adapt to living away from the Earth? Will we become denizens of many worlds, or will we (and possibly extraterrestrials, as well) always be restricted to the planet of our origin?
THE ASTROBIOLOGY INSTITUTE
With these ambitious goals in hand, in 1997 the Ames group presented their plan for astrobiology to Dan Goldin, NASA’s chief administrator. Goldin enthusiastically supported the idea. Not only was he personally excited by the search for life on other worlds, he was also shrewd enough to understand that such a program could capture the imagination of the general public—which would mean more support for NASA by the taxpayers and, in turn, by the politicians who decide NASA’s budget.
Moreover, the Ames approach did not call for the usual bricks-and-mortar of new facilities and organizational empire-building. Instead, the plan was to create an Astrobiology Institute to serve as a focal point for the research and enlist the talents of already existing research organizations in academia, industry, and government. Taking advantage of Ames’ expertise in electronic information systems, the Institute would be a “virtual” organization with a bare-bones staff, linked to the various research groups around the country and overseas by electronic communications.
